1. Field of the Invention
The invention relates to a single-piece vent or drain pipe coupling of the type which has a flexible bellows-type central portion.
2. Description of the Prior Art
Vent or drain pipes having a bellows-like center section are disclosed in German Patent DE-PS 29 29 978. Such vent or drain couplings offer the advantage that they can be deformed in a manner to go around obstacles in the roof support framework that cannot be moved or eliminated for many reasons. These couplings can also be used if the conduits that have to be connected with the hose are displaced axially. Installations with highly limited space availability usually require the simplest possible connector design between the parts to be joined. Also, a good seal is required between the parts joined which seal must be capable of functioning over very long service periods. For this purpose, the above-mentioned known coupling uses a separate rubber seal ring between a connection end attached to the roof vent, and a pipe receiving end for retaining the end of the connection pipe.
The receiving end of the flexible pipe coupling has an internal annular groove for accommodating the rubber seal ring. These sealing measures do not always function in an entirely reliable manner. Mainly if they are installed dry or with unfavorable tolerances on mating parts, the leading edge of the short connection pipe in the roof vent may push the seal ring out of its groove during insertion. Furthermore, the installer may forget to install a seal ring. This results in a potential hazard when making the connection between the short roof vent connection pipe and the receiving end of the flexible coupling which is not immediately noticeable because the seal cannot be seen. If the seal ring is not present the interconnection gradually becomes detached so that the problem may not be noticed for a long time with the result that the waste water or gases are not properly discharged. In addition, rain and condensation will readily enter the area of the roof framework. Since the seal ring is a separate part, it is particularly annoying if the seal ring slips from the installers hand such that the seal ring drops from the roof onto lower floors of the building resulting in a troublesome search.